Loud-speaker unit



lJuly 30, 1929 G. F. BOR'KMAN LOUD SPEAKER UNIT Filed Feb. 2, 1927 Patented July 30, 1929.

Parana orifice.

' GEORGE F. isonKMAN, or sAL'r LAKE crTY, -UTAH.

LOUD-SPEAKER UNIT.

Application filed February a, 1927. serial No. 165,413.

This invention relates to an electromagnetically actuatedloud speaker unit and its principal objects are to provide an instrument which shall:

First. Be highly efficient.

Second. Have means whereby the magnetic flux density operative upon the armature, may be moreA characteristics of any particular diaphragm 1o than is ordinaril the case. y

Third. Have t e pole pieces arranged for a large area of contact with the permanent magnet.

Fourth. Lessen to a considerable' degree, the liability of freezing to the pole pieces.

Fifth. Be simple to assemble, and therefore economical to manufacture.

In attaining these objects, I use preferably a permanent magnet of U-shape with pole ZOpieces mounted along the inside faces of the legs thereof. The pole'pieces are preferably of similar shape, and reversed in position, relatively to each other.

The pole pieces consist, each, of a bar with depending flanges along two opposite edges thereof, while on the third edge is a bracket which extends away from the bar and along the flanges, the flanges and bracketbeing in'- tegral with the bar. The outer surface of the bracket and the end face of the flanges adjacent thereto, are preferably in the same plane, and form a surface of contact against the permanent magnet. The spool may be mounted between the bars and between the flanges of the two pole pieces, while the armature, as usual, may be oscillatingly mounted in the sleeve of the spool. Both flanges of each pole piece are bifurcated, for two purposes, (a) to bring the longitudinal center line of the pin w ich connects the armature to the diaphragm, closer to the center of oscil- V lation of the armature; and (b) to better con- 'trol the magnetic 'flux passing through the armature. s

By making the gap betweenthe flanges of the pole pieces at one end ofthe armature, greater than the gap at the otherl end of the armature, the armature is less likely to freeze to the pole pieces.

The features of this invention for which the protection of Letters Patent is desired, are collectively grouped in the claims concluding this speci cation.

In the drawing, which illustrates one em- 55 bodiment of my invention,

Fig. 1 represents a plan;

nearly proportioned to the Fig. 2, the' same, with parts broken away to show a section, principally upon line 2-2, F1g.-3, the spool, however, being in section on the .center plane thereof; f

Fig. 3, an elevation in the direction of arrow 3, Fig. 1;

4, a section on line 4-4 Fig. 1; F1g. 5, a detail, in perspective, of a pole piece, the interiorthereof being exposed. to View; t

Fig. 6, a fragmentary diagram enlarged, showing the relationship between the armature and the pole pieces;

Fig. 7 a plan of the armature alone. Referring to the drawing, 20 indicates the cap, 21 the plate, and 24 the locking ring for clamping the'cup and cap together, the diaphragm 25 being interposed, all in accordance with my co-pending application for U.

'i S. Patent, Serial N o. 165,412, the ling date of which is even herewith. The' plate 21 carries integral placement members consist; ing of the lugs 26, and the stops 27. The U- shaped permanent magnet 38 rests with one of its U-faces on the upper surface of the cap 21, being positioned in assembling by the stops 27 and the lugs 26, and held between the latter by means of the screws 29 which pass through the lugs 26, through the respective legs of the magnet, and finally, are threaded in the brackets 41 of the pole pieces.

The spool 31 with its' coil 32, is held between the -bars 43 and flanges 45 of the pole pieces. The armature 28 may be eccentrically pivoted at 35 in the sleeve of the spool and be connected to the diaphragm by the duplex pin connection consisting of the primary part 30 and the bent auxiliary part 301, as disclosed in my pending application for U. S.' patent, filed August 23, 1926, Serial No.

An important part of the present invention consists 1n bifurcating the flanges 45 of the pole pieces by cutting the transverse slots 50, defined by the forward flange portions 45l and the rearward flange portions 452. This construction is particularly advantageous for use in conjunction with theduplex pin just escribed, as it enables me to bring the points where the two branches of the pin are connected to the armature, much closer to the center of oscillation, than is the case where the connections are made to the armature outside theouter flange planes of the pole pieces. Bythus bringing the lines of action of the pins nearer the center of oscillation of the armature, the lever arms of the armature, which perform the work, are shortened, and the force transmitted by .the armature to the diaphragm, correspondingly increased.

By referring to Fig. 4, it will be noticed that the pin connections to the armature substantially coincidewith the centers of application of the magnetic flux from the pole pieces to the diaphragm. Thus, the power arms and work arms of the armature are substantially equal to each other, which is not the case when the pin connections to the diaphragm lie outside the outer face planes of the pole piece fianges. l

The other advantage which accrues tl'irough the bifurcated arrangement of the pole piece flanges, is the fact that the width of the slots, indicated by the arrows 51, Fig. 5, may be varied, thereby varying the amount of magnetic flux that is concentrated upon the armature. In this way, if a heavy diaphragm is used, a greater force can be concentrated upon it, by making the width of the slot correspond to the result desired. Again, if a lighter diaphragm is used, the force operative upon it may be correspondingly lessened.

By means of the brackets 4l, together with the end faces of the flanges 45, the area of contact between the pole pieces and the pervmangent magnet 38, i-s rendered comparatively large, so that the magnetic flux will pass freely from one to the other.

The fact that the pin connections from the armature lie inside the outer surfaces of the pole piece flanges, enables me to 'make the armature purely rectangular in shape without any projecting ears, thereby not only simplifying the manufacture and reducing the cost of production, but actually increasing the power of the armature by reducing Jihe dead load to be moved by the magnetic v One of the gaps between the pole pieces, in this instance the one at 52, is made somewhat greater than the other one, in order that the armature in vibrating, shall at n0 time simultaneously touch two pole pieces.

Although my duplex pin connectionfrom the armature to the diaphragm is specifically shown herein, it will be obvious that the present invention can be advantageously used with any ordinary pin connection.

As it is old in the art to associate permanent magnets with pole pieces, electromagnet coils, and oscillating armatures, and also, to connect armatures to diaphragms by means of pins, I assert no novelty for the mere association of such elements with one another, but limit my invention to the unique features of the pole pieces as herein disclosed, or their equivalents. and to the unique combinations thereof with the other elements as defined in the claims that presently follow.

lVhile a particular embodiment of this invention is herein shown and described, it must be clearly understood that the detailed parts thereof, may or may not, appear in the preferred forms, and also, that the preferred forms may be varied from time to time, depending upon the circumstances and conditions governing and governed by, the development of this invention and the arts to which it is incident, therefore its scope is broadly stated in the claims.

Having ful-ly described my invention, what I claim is:

l. A permanent magnet, pole pieces extending from vthe poles thereof with flanges in mutually overlapping relation, a vibrating armature operativel disposed between said pole pieces, and a bifurcation defined in each of the flanges of the said pole pieces.

2. A permanent magnet, pole pieces extending from the poles thereof, said Dole pieces having flanges in cooperative relation, an armature mounted for operation between said flanges, and bifurcations defined in the saidflanges where said flanges are operative on said armature. l

3. A permanent magnet, pole pieces eX- tending from the poles thereof, said pole pieces having flangesvextending' towards and in cooperative relation to each other, and an armature mounted for operation between said flanges, the operative effect of said pole pieces on said armature being'modified by bifurcations defincd in said flanges.

4. A permanent magnet, pole pieces having flanges extending from the poles thereof in cooperative relation to each other, bifurcations defined in said flanges, and an armature mounted between said fianges.

5. A permanent magnet, pole pieces having flanges extending from the poles thereof in cooperative relation to each other, an armature mounted in operative relation to said pole pieces, bifurcations defined in said flanges, said bifurcations being located to modify the eect of the pole pieces on the armature, and a diaphragm connected to said e armature.

6. A permanent magnet, pole pieces in contact therewith, said pole pieces having two pairs of flanges extending mutually towards each other, thereby defining gaps between them, and an armature poised so as to have one end thereof positioned in one gap, and the other end thereof positioned in the other gap, one of the said gaps being of greater extent on either side of the center position of the said armature, than the other gap.

7. A permanent magnet, pole pieces in contact therewith, said pole pieces having two pairs of flanges exten-ding mutually towards each other, said flanges being bifurcated, gaps defined between said pole pieces, and an armature poised so as to have one end thereof positioned in one gap, and the other end thereof positioned in the other gap, one of the said bifurcated flanges extendin I from the poles thereof in cooperative relatlon to each other,

an armature mounted for-operation between said pole pieces, a diaphragm operativey positioned, and a connecting member exten ing from the armature to the diaphragm, the said connecting member being positioned in the space mutually deined'by the bifurcated portions of said anges. l

' 9. A permanent magnet, pole pieces having bifurcated flanges extendmg from the poles thereof in'cooperative relation to each other,

an armature mounted for operation between said pole pieces, a diaphragm operatively positioned, and a duplex pin extending from the armature to the diaphragm, the4 said duplex in being positioned in the space mutually ened by thebifurcated portions of said flanges.

10. A U-shaped permanent magnet, pole pieces connected to the legs thereof in mutually reversed relation, said pole pieces comprising each, a bar with depending bifurcations defined in said flanges, and an armature poised in the gap) between said flanges' so as to be influenced y the magnetic flux passing through said bifurcated portions. i f

11. A source of magnetism, pole pieces ara'nges,

ranged vto conduct flux thereof, said pole pieces extending mutually toward each other, and an armature operatively mounted between saidfpole pieces, said pole pieces having eachpolar extremity thereof bifurcated in a manner to modify the effect of the magnetic flux upon the corresponding extremity of said armature.

12; A source of magnetism, a vibrating armature iniiuenced along its polar extremities by iux from said source, and means for bifurcating the flux at each of the said extremities of the armature. y

13. A pole piece comprising a depending from opposite sides and transverse slotsdeined in the said anges. f In testimony whereof, I sign my name here- GEORGE F. BORKMAN.

bar, flanges of said bar, l 

